Arthroscopic features of primary and concomitant flexor enthesopathy in the canine elbow

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Original Research

Arthroscopic features of primary and concomitant flexor enthesopathy in the canine elbow E. de Bakker; Y. Samoy; E. Coppieters; L. Mosselmans; B. Van Ryssen Ghent University, Department of Medical Imaging and Small Animal Orthopaedics, Merelbeke, Belgium

Keywords Flexor enthesopathy, arthroscopy, diagnosis, elbow, dog

Summary Objectives: To investigate the possibilities and limitations of arthroscopy to detect flexor enthesopathy in dogs and to distinguish the primary from the concomitant form. Materials and methods: Fifty dogs (n = 94 elbow joints) were prospectively studied: dogs with primary flexor enthesopathy (n = 29), concomitant flexor enthesopathy (n = 36), elbow dysplasia (n = 18), and normal elbow joints (n = 11). All dogs underwent an arthroscopic examination of one or both elbow joints. Presence or absence of arthroscopic characteristics of flexor enthesopathy and of other elbow disorders were recorded.

Correspondence to: Evelien de Bakker, DVM, PhD Ghent University Department of Medical Imaging and Small Animal Orthopaedics Salisburylaan 133 Merelbeke, 9820 Belgium Phone: +32 9 264 7650 Fax: +32 9 264 7793 E-mail: [email protected]

Results: With arthroscopy, several pathological changes of the enthesis were observed in 100% of the joints of both flexor enthesopathy groups, but also in 72% of the joints with elbow dysplasia and 25% of the normal joints. No clear differences were seen between both flexor enthesopathy groups. Clinical significance: Arthroscopy allows a sensitive detection of flexor enthesopathy characteristics, although it is not very specific as these characteristics may also be found in joints without flexor enthesopathy. The similar aspect of both forms of flexor enthesopathy and the presence of mild irregularities at the medial coronoid process in joints with primary flexor enthesopathy impedes the arthroscopic differentiation between primary and concomitant forms, requiring additional diagnostic techniques to ensure a correct diagnosis.

Vet Comp Orthop Traumatol 2013; 26: ••–•• doi:10.3415/VCOT-12-09-0111 Received: September 7, 2012 Accepted: February 1, 2013 Pre-published online: May 27, 2013 Funding source: BOF grant 01D31908

Introduction Thoracic limb lameness in medium and large breed dogs is often localized in the elbow joint. The most important cause is elbow dysplasia, which is a collective term for medial coronoid disease, osteochondritis dissecans of the humeral condyle, ununited anconeal process, and joint incongruity (1-5). Flexor enthesopathy is a

recently recognized elbow disorder and is considered an important differential diagnosis for elbow dysplasia (6-8). It is defined as an abnormality of the medial humeral epicondyle and the attaching flexor muscles, radiographically seen as a calcified body or a spur (6-15). In the past, these radiographical changes were often considered as coincidental or clinically unimportant findings (6, 7, 14). However, a re-

cent study has demonstrated the relatively frequent occurrence of medial humeral epicondylar changes (8). Most cases of flexor enthesopathy are described concomitantly with other elbow disorders, mainly medial coronoid disease (7-9, 11). The challenge in these cases is to define the cause of the elbow pain in order to perform the correct treatment. In a small percentage of cases, flexor enthesopathy occurs as the only finding and is therefore considered as the primary cause of elbow lameness (8). Primary flexor enthesopathy can occur with clear radiographic changes, however a recent study demonstrated the presence of obscure forms of primary flexor enthesopathy with minimal or even absent radiographic changes (7). Therefore radiography can be used as a first screening method for the detection of flexor enthesopathy, but diagnosis may be missed, or confusion with discrete forms of medial coronoid disease may occur. Additional more sophisticated imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), both with IV contrast, and scintigraphy are sensitive techniques to detect flexor enthesopathy. However, these techniques are unable to differentiate between primary flexor enthesopathy and the concomitant form (16-20). The identification of both forms of flexor enthesopathy is necessary because of the different treatment approaches. In case of primary flexor enthesopathy, an intra-articular injection of methylprednisolonacetate is given or the affected flexor muscle is surgically transected; both methods of treatment are derived from human medicine (6, 7, 21). The authors’ current treatment approach to concomitant flexor enthesopathy is the sura

Richard Wolf GmbH, Knittlingen, Germany

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E. de Bakker et al.: Arthroscopy of primary and concomitant flexor enthesopathy

gical removal of the fragment or flap related to the elbow dysplasia. Arthroscopy is a widely accepted diagnostic and treatment method for medial coronoid disease of the canine elbow joint (22-25). Because arthroscopy allows the direct visual inspection of the articular surface, it can provide information that is not available with radiography or clinical examination; both are the most frequently used diagnostic techniques in veterinary medicine (25, 26). The results of a preliminary study showed that arthroscopy can also be used for the diagnosis of flexor enthesopathy in dogs (16). In that same study however a detailed analysis of the specific arthroscopic findings consistent with flexor enthesopathy was not performed (16). The aim of this study was to examine the possibilities and limitations of arthroscopy to detect flexor enthesopathy and to distinguish primary flexor enthesopathy from the concomitant form.

Materials and methods A prospective study was performed on 50 dogs (n = 50) according to the guidelines of the Animal Care Committee of Ghent University (Merelbeke, Belgium). All dogs, except for the normal control dogs, were presented with the complaint of thoracic limb lameness at the Veterinary University Clinic of Ghent University. All dogs underwent an arthroscopic examination together with additional radiographic (n = 50), ultrasonographic (n = 48), scintigraphic (n = 45), CT (n = 50), and MRI (n = 49) examinations for diagnostic purposes as well as to obtain the criteria to characterize the dogs. The elbow joints of the 50 dogs were divided in four groups based on the final diagnosis obtained with the different imaging modalities. The elbow joints of nine dogs had different lesions and were assigned to two different groups (▶ Table 1).

Table 1 Breed distribution within the four groups of elbow joints. Breed

Total of Primary dogs flexor enthesopathy (joints)

Concomitant flexor enthesopathy (joints)

Elbow dysplasia (joints)

Normal joints (joints)

Labrador Retriever

12

4

10

8

0

Great Swiss Mountain Dog 5

7

1

0

1

Bernese Mountain Dog

3

0

4

1

0

Rottweiler

5

5

4

0

0

Golden Retriever

5

2

4

2

2

Mixed Breed

3

4

2

0

0

Swiss Shepherd Dog

1

0

1

0

0

Border Collie

1

2

0

0

0

French Bull Dog

1

0

0

0

1

Newfoundlander

5

3

5

0

0

Saint Bernard Dog

1

0

1

1

0

Dutch Partridge Dog

1

2

0

0

0

Bouvier

1

0

2

0

0

Bullmastiff

1

0

2

0

0

Shepherd Dog

1

0

0

2

0

Appenzeller

1

0

0

2

0

English Cocker Spaniel

1

0

0

2

0

Fox Hound

2

0

0

0

4

Total

50

29

36

18

8

Group 1: Primary flexor enthesopathy Group 1 consisted of 29 elbow joints of 17 client-owned dogs between seven and 92 months old (median 56.4 months). Eleven dogs were male and six were female. Twenty-two elbow joints were clinically affected and seven elbow joints were clinically unaffected since no signs of elbow pain or lameness were found. Therefore these seven joints were considered subclinically affected. Dogs were included in this group when at least three of the five imaging modalities demonstrated lesions consistent with flexor enthesopathy (7, 16, 17). Radiographic signs were an irregular outline of the medial humeral epicondyle, a spur and a calcified body. Ultrasonographic findings were an abnormal fibre structure, an abnormal attachment, an irregular outline of the medial humeral epicondyle, the presence of a calcified body, and outward bowing. The scintigraphic sign was increased radiopharmaceutical uptake in the area of the medial humeral epicondyle. Computed tomographic features were an irregular thickened sclerotic medial humeral epicondyle, thickened flexor muscles with contrast uptake, and a calcified body. The MRI features were an irregular sclerotic medial humeral epicondyle, thickened flexor muscles with contrast uptake, and a calcified body. Dogs included in group 1 also had no evidence of other elbow disorders based on CT and arthroscopy.

Group 2: Concomitant flexor enthesopathy Group 2 consisted of 36 elbow joints of 24 client-owned dogs between seven months and 104.4 months old (median 50.4 months). Seventeen dogs were male and seven dogs were female. Thirty joints were clinically affected and six joints were considered subclinically affected. Dogs were included in this group when flexor enthesopathy lesions were identified with at least three imaging modalities and the additional presence of medial coronoid disease (n = 29), osteochondritis dissecans (n = 3), or both lesions together was confirmed with CT and arthroscopy (7, 16, 17).

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E. de Bakker et al.: Arthroscopy of primary and concomitant flexor enthesopathy

Group 3: Elbow dysplasia Group 3 consisted of 18 elbow joints of 13 client-owned dogs, all clinically affected. The age was between 10 months and 126 months (median 34.8 months). Eight dogs were male and five were female. In all dogs, flexor enthesopathy was excluded based on five imaging methods, and the presence of elbow dysplasia was confirmed based on arthroscopy and at least one of the four other imaging modalities (7, 16, 17).

Group 4: Control, normal joints Group 4 consisted of two laboratoryowned and three client-owned dogs. The age was between 19 months and 126 months (median 64.8 months). This group consisted of three male dogs and two female dogs. For this group, eight elbow joints were included in the analysis based on absence of elbow lesions using radiography, ultrasonography, scintigraphy, CT or MRI. The breed distribution for the four groups of dogs is illustrated in ▶ Table 1.

Figure 1 Arthroscopic images illustrating the approach of the flexor muscles and their attachment to the medial humeral epicondyle. Following the ulnar trochlear notch (1) with the viewing angle directed upwards in the direction of the medial humeral epicondyle (black arrowhead), the attaching flexor muscles can be visualized (2). 3 = Medial part of the humeral condyle, 4 = Anconeal process.

Arthroscopy Arthroscopy was performed with a 2.4 mm, 25° fore-oblique arthroscopea. Prior to arthroscopy, dogs were sedated using acepromazineb (0.01 mg/kg, IV) and medetomidinec (28 μg/kg, IV) and then anaesthetized with propofol (6 mg/kg, IV). After intubation, anaesthesia was maintained with isoflurane in oxygen. Dogs were positioned in lateral recumbency with the examined elbow close to the operating table and extended. The elbow joint was arthroscopically inspected via a medial approach (27). The intra-articular structures were inspected and specific regions within the elbow joint were visually assessed. By moving the arthroscope towards the ulnar trochlear notch and rotating the viewing angle towards the medial humeral epicondyle (viewing angle directed upwards), the flexor muscles and their entheses were vis-

b c d

Placivet: Codifar, Wommelgem, Belgium Domitor: Pfizer Animal Health, Brussels, Belgium Rimadyl: Pfizer S.A., Louvain-La-Neuve, Belgium

Figure 2 Arthroscopic images illustrating a fibrillated (A-C) and ruptured (D-F) insertion of the flexor muscles to the medial humeral epicondyle. A-C: Minimal (A) – clear (B, C) fibrillation visible, characterized by loose, shiny (black arrow), undulated fibres (white arrowhead). D-F: Ruptured insertion characterized by a cleaved appearance of the flexor muscles (D) and ruptured pieces of flexor muscles (E, F) (black arrow).

ually assessed (▶ Figure 1). Digital still and video images of the arthroscopic procedure in all elbows were recorded. Each arthroscopic image was evaluated by consensus by the first author (EdB) and an experienced orthopaedic surgeon specialized in arthroscopy (BVR). The presence or absence of the following arthroscopic characteristics of flexor enthesopathy were recorded: fibrillated or ruptured insertion of the flexor muscles, local synovitis and a cartilage erosion near the insertion site,

and a thickened and yellow discoloured appearance of the flexor muscles. A fibrillated insertion was characterized by the presence of loose, shiny, undulating fibres, while in a ruptured insertion pieces of the flexor muscle were visible or the flexor muscle appeared to have been cleaved (▶ Figure 2). Thickening of the flexor muscles was evident as white and swollen tissue (▶ Figure 3). Arthroscopic characteristics of the medial coronoid process (▶ Table 2), ap-

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E. de Bakker et al.: Arthroscopy of primary and concomitant flexor enthesopathy

Table 2 Detailed description of the arthroscopic findings of different types of medial coronoid process lesions (27). Medial coronoid process diagnosis

Detailed arthroscopic findings of the medial coronoid process

Chondromalacia

Irregular, soft or fibrillated cartilage. No fissure.

Fissure

Cartilage fissure or irregular, soft or fibrillated cartilage. No mobile fragment when probing.

Non-displaced fragment

Complete fissure. Fragment located at its original position and mobile when probing.

Displaced fragment

Fragment cranially displaced.

Medial compartment erosions

Erosions of the medial coronoid process. No fragmentation, except cartilaginous mini-fragments smaller than 2 mm.

Table 3 Modified Outerbridge scoring system, used for the arthroscopic evaluation of the cartilage condition of the medial part of the humeral condyle (27).

pearance of the medial part of the humeral condyle (osteochondritis dissecans, cartilage lesions scored according to the modified Outerbridge classification system [▶ Table 3]), and presence or absence of incongruity were also recorded (28). Carprofend (50 mg/ml IV) was administered to all dogs during the arthroscopic procedure except for dogs with primary flexor enthesopathy, which were treated with an intra-articular injection of methylprednisolonacetatee (0.5-2 mg/kg bodyweight). All treated dogs of the elbow dysplasia and concomitant flexor enthesopathy groups, and all surgically treated dogs of the primary flexor enthesopathy group, had an additional intra-articular injection of mepivacaine hydrochloridef at the end of the procedure. A light pressure bandage was applied on the elbow. All dogs except the those with primary flexor enthesopathy, which were treated by an intraarticular injection of methylprednisolonacetate, were treated with carprofen (50 mg/ml for three weeks) postoperatively. For all dogs, restricted exercise with leash walks was advised.

Modified Outerbridge score

Arthroscopic description of the medial humeral cartilage condition

0

Normal cartilage

1

Chondromalacia (cartilage with softening and swelling)

2

Partial thickness fibrillation Superficial erosions with pitting or a ‘cobblestone’ appearance Lesions that do not reach the subchondral bone

3

Deep ulceration that does not reach the subchondral bone

Data Analysis

4

Full thickness cartilage loss with exposure of the subchondral bone

5

Eburnated bone

Fisher’s exact test was used to compare the arthroscopic characteristics of flexor enthesopathy between dogs affected by primary flexor enthesopathy and dogs affected by concomitant flexor enthesopathyg. The significance level was set at p